[The meaningfulness of central venous blood samples. Central venous versus mixed venous O2 status]

Both mixed-venous and "central-venous" oxygen status (O2 partial pressure [pO2], O2 saturation [sO2], O2 concentration [cO2], hemoglobin concentration [cHb]) are often considered to adequately represent total-body oxygen supply. Since modern technology has made continuously in vivo measurement possible, mixed-venous O2 saturation (svO2) and partial O2 saturation (psO2) have become extensively used for that purpose. Both venous sites of measurement are used as diagnostic adjuncts regarding hemodynamic status. However, both are associated with certain problems. There is a lack of any clear definition of a "central-venous" site of the catheter tip (right atrium, superior vena cava, inferior vena cava). Instead, the location of the catheter tip depends upon the approach to the central venous system. One must also be aware of significant migrational tendencies of the catheter tip. Thus, "central-venous" samples can only represent the situation in a single portion of the circulation, whereas the respective organ areas may vary considerably with the same catheter from one time point to another. Furthermore, the state of the coronary circulation never can be evaluated. The frequently postulated correlation of mixed-venous and "central-venous" values decreases with increasing deterioration of the cardiovascular system, especially in patients with high cardiovascular risks. The main overall parameters of mixed-venous oxygen status are oxygen content (cvO2), cardiac output (C.O.), and oxygen consumption (QO2) of the tissues. The relation between arterial and mixed-venous O2 status is given by Fick's principle: caO2-cvO2 = QO2/C.O. From this, it becomes obvious that a relation between cvO2 and C.O. may only be presumed if QO2 and caO2 remain constant. Evaluation of O2 availability (AO2) using cvO2 or the determining components of cvO2 seems reasonable only if the modulating influences of C.O. and QO2 are taken into consideration. Therefore, any empirically deduced relation between svO2 and C.O. (regardless of the origin, i.e., linear or nonlinear) must be viewed as being accidental. This implies that svO2 and cvO2 per se are only partly helpful in evaluating the hemodynamic situation. The best parameters for interpreting the cardiovascular situation seem to be arteriovenous O2 difference (avDO2) and C.O. In particular, the avDO2 can be accepted as an integrating parameter for AO2 and QO2, and may therefore serve as a diagnostic indication of cardiovascular imbalance.

Simultaneous transcranial Doppler sonography and cerebral blood flow measurements of cerebrovascular CO2-reactivity in patients with aneurysmal subarachnoid haemorrhage

Transcranial Doppler sonography (TCD) flow velocities and cerebral blood flow (CBF) measurements were evaluated in 14 patients who had suffered a major aneurysmal subarachnoid hemorrhage (SAH). Cerebrovascular reactivity to hypocapnia was evaluated simultaneously by the two methods. The measurements were performed under general anaesthesia preoperatively, within 72 hours after the bleed, during normocapnia and hypocapnia. There was poor correlation between absolute values of hemispheric CBF and corresponding TCD mean flow velocity. Controlled hyperventilation was associated with a significant decrease in CBF as well as TCD flow velocity (p less than 0.001). In terms of reactivity indices the correlation between the two methods was poor and not significant (r = 0.33, p = 0.09). The principal differences between the methods are discussed as well as the application of TCD in the evaluation of cerebrovascular reactivity.

Does nimodipine eliminate arterial hypertension as a prognostic risk factor in subarachnoid haemorrhage?

Several studies have demonstrated an association between arterial hypertension (AH) and an increased morbidity and mortality from both cardiovascular diseases and stroke (including subarachnoid haemorrhage, SAH). Among the functional disturbances implicated in hypertension much interest has been focused on the calcium handling in the vascular smooth muscle cells, and it has been proposed that a defect in the calcium gating mechanisms in the cell membrane is of major importance. Clinical trials have confirmed that calcium antagonists of the dihydropyridine type (nimodipine) are useful in preventing secondary ischaemia after SAH. The purpose of this retrospective study was to determine if the protective effect of nimodipine differs between normotensive and hypertensive patients focused on delayed ischaemia, total morbidity and mortality. In the group (137 patients) without nimodipine treatment 17 out of 31 individuals (55%) with AH had an unfavourable outcome. In the nimodipine group (also 137 patients) four out of 25 individuals (16%) with AH had an unfavourable outcome. In terms of vasospasm and delayed ischaemia only, the difference was even more evident. These results indicate that nimodipine seems to significantly reduce the prognostic difference between normo- and hypertensive individuals with an aneurysmal SAH.

A simple technique of posterior wiring in traumatic instability of the mid to lower cervical spine. Technical note

Wiring without bone fusion in the treatment of traumatic cervical instability is an uncommon procedure. The authors describe a semirigid wiring technique for stabilizing the acute injured movement segment in the mid and lower cervical spine. Results are briefly discussed.

Heat production rate in blood lymphocytes as a prognostic factor in non-Hodgkin's lymphoma

The heat production rate in peripheral blood lymphocytes was evaluated by direct calorimetry in 76 untreated adults with non-Hodgkin's lymphoma (NHL). Elevated values were recorded for 20 out of 54 patients with lymphomas of high or intermediate malignancy grade (37%) and for 1 out of 22 patients (5%) with low grade lymphomas (p = 0.01). Median survival was 39 months for patients with normal values and 8.5 months for those with elevated values (p = 0.005). In a subgroup of 38 patients with high or intermediate grade NHL stage III-IV, 17 patients with abnormally high lymphocyte heat production rates had a significantly shorter survival than 21 patients with normal values (p = 0.01). In a multivariate analysis the prognostic impact of lymphocyte heat production was superior to histologic malignancy grade, clinical stage and age.

[Analgesia and sedation in neurosurgical intensive care patients]

Different concepts for analgosedation of neurosurgical patients are recommended during postoperative ventilation. In 30 neurosurgical patients (2 groups of 15 patients), we studied a continuous i.v. application of alfentanil (Rapifen) and midazolam (Dormicum) compared to an application of continuously given alfentanil with discontinuously given midazolam. A good analgosedation (i.e. sufficient sedation with good neurological judgement) was more frequently achieved (8/15 patients) by continuous application of both substances (alfentanil 0.023 mg/kg b.w./h, midazolam 0.10 mg/kg b.w./h), compared to discontinuous application of midazolam (4.5/15 patients; alfentanil 0.028 mg/kg b.w./h, midazolam 0.13 mg/kg b.w./h). No differences in extubation times were observed. We conclude from our results that a continuous application of both substances is superior to a discontinuous application of midazolam with continuously given alfentanil. A lower dosage of each substance is necessary to maintain a better state of analgosedation.

Correlation of transcranial Doppler sonography findings with timing of aneurysm surgery

Thirty-six patients with a proven first subarachnoid hemorrhage (SAH) from a ruptured supratentorial aneurysm were subjected to repeated transcranial Doppler sonography assessments. Eighteen individuals (Group A) were operated on within 48 hours, while the other 18 (Group B) had surgery between 49 and 96 hours after SAH. The patients represented two clinically comparable groups. In the first 72 hours post-SAH, no increased flow velocities suggestive of arterial narrowing or vasospasm were recorded. There was no significant difference in preoperative flow velocities between the groups. Postoperative flow velocities were significantly lower in patients operated on within 48 hours (p less than 0.001). Two patients, who had surgery on Day 4 post-SAH and who showed the highest recorded postoperative flow velocities, died from cerebral vasospasm and infarction. The results favor a referral system which enables early surgical intervention not only to prevent rebleeds but also aimed at reducing delayed ischemic dysfunction.

Low birthweight, congenital malformations, and spontaneous abortions among dry-cleaning workers in Scandinavia

With a common study protocol, case-referent studies within cohorts were performed in Denmark, Norway, Sweden, and Finland to study reproductive hazards of women doing dry-cleaning work. Due to national differences not all of the studies could follow exactly the same procedures in data collection, but they were all based on the linkage of cohorts of dry-cleaning and laundry workers to national registers of births and reproductive failures. Summary measures from each study were combined without the data being pooled. The most significant finding was an increased risk of spontaneous abortion among the most exposed women in the Finnish data. This finding was only supported by the results of the other studies to a minor degree, and the combined odds ratio had confidence limits which included unity.

Early aneurysm surgery and preventive therapy with intravenously administered nimodipine: a multicenter, double-blind, dose-comparison study

A European, multicenter, prospective, randomized, double-blind, dose-comparison study on preventive therapy with intravenously administered nimodipine was performed to evaluate the efficacy and tolerability of two different doses: 2 and 3 mg/h. Two hundred four patients fulfilled the criteria for enrollment in the study: surgery within 72 hours after the last subarachnoid hemorrhage, and age between 16 and 72 years. All patients who had Hunt and Hess grades of I to III were operated upon; patients who had poor Hunt and Hess grades (IV-V) were operated on according to the surgeon's choice. This treatment regimen was associated with a low incidence of delayed neurological dysfunction with no significant difference between the two dosage groups: three patients (1.5%) remained severely disabled and two (1%) moderately disabled due to vasospasm with or without additional complications. Among the patients with Hunt and Hess grades of IV or V, the long-term outcome was favorable (good-fair) for 40% and unfavorable for 60%. Among the patients with grades of I to III, the long-term outcome was favorable for 89% and unfavorable for 11%.

Mitotic activity and survival in advanced non-Hodgkin's lymphoma of unfavourable histology

The number of mitoses per high power field (mitotic index, MI) was assessed in 2 microns sections of lymph node biopsies from 58 adults with non-Hodgkin's lymphoma. All had diffuse nodal lymphomas of unfavourable histology and stage II-IV disease. The patients were treated with chemotherapy and followed for a minimum of 3 years or until death. None out of 29 patients with a MI greater than or equal to 3.0 survived for 3 years after diagnosis whereas 13 out of 29 other patients with MI less than 3.0 became long-term survivors (P = 0.00002). Differences in age, sex or clinical stage between short- and long-term survivors were negligible. The initial chemotherapy regimens were not more intense for the long-term survivors. Twenty-nine patients were given an equivalent initial treatment with CHOP or CHOP plus methotrexate. The association between MIs and survival was evident also in this subgroup. The results indicate that survival is extremely poor for patients with advanced diffuse nodal lymphomas of unfavourable histology and a high mitotic count. It seems especially important to evaluate alternative chemotherapy regimens, suggested to be more effective than current programmes, in this subset of patients.

Cognitive functioning after subarachnoid haemorrhage of unknown origin

Twenty patients, who had sustained a proven subarachnoid haemorrhage (SAH) and in whom cerebral panangiography had failed to reveal any source of the bleeding (SAH-NUD), were subjected to a neuropsychological examination involving memory functions, spatial perceptual organization, visuoconstructive abilities, reasoning, perceptual speed and accuracy, and concept formation. Cognitive functioning in SAH-NUD patients was compared with normal reference values and also related to the cognitive performance of neurologically intact patients having sustained an aneurysmal bleeding (SAH-AN). SAH-NUD patients showed significant reduction of verbal learning and retention, and of abilities involving abstract attitude and concept formation, i.e., functions related to frontotemporal structures. In all other respects the performance of these patients approached normality. Unexpectedly, there were no significant differences in mean test scores separating SAH-NUD from aneurysmal SAH patients. Collapsing the patient groups produced an increased number of significant deviations from normality, which was interpreted as the effect of the contribution of a greater number of relatively more impaired SAH-AN patients. This was supported by the finding that the ratio of impaired individuals to total number of subjects differed in the groups; the proportion of individuals showing cognitive sequelae was larger among SAH-AN patients throughout all comparisons but one. Although SAH of unknown aetiology represents much less of a catastrophe as compared with haemorrhage of aneurysmal origin, it does not preclude cognitive disturbances. Thus, the presence of blood per se anywhere in the subarachnoid spaces appears to affect higher brain function(s).

Late magnetic resonance imaging related to neurobehavioral functioning after aneurysmal subarachnoid hemorrhage

Twenty patients who underwent early aneurysm surgery--that is, surgery within 72 hours after rupture--underwent further follow-up examination including magnetic resonance imaging (MRI) of the brain and a comprehensive neuropsychological assessment. Significant statistical correlation between tissue loss as seen on a late MRI scan and neurobehavioral deficits could not be established. Among 9 patients with no tissue loss seen on MRI, 3 exhibited substantial cognitive dysfunction and 6 had mild impairment. Three patients showed minor but corresponding tissue loss and deficits. In 3 patients with pronounced pathological indications on MRI, evidence of cognitive dysfunction was absent in 2, and 1 patient showed substantial impairment. The remaining 5 individuals displayed moderate pathological indications on MRI, with no obvious correspondence to cognitive functioning. In 7 patients, small white matter lesions, probably silent infarcts not seen on computed tomographic scan, were discovered on MRI. There was a clear relationship between arterial hypertension prior to aneurysm rupture and the extent of tissue loss seen on MRI. Absence of pathological findings on MRI scan did not exclude cognitive malfunctioning, and vice-versa.

Arterial and mixed venous blood gas status during apnoea of intubation--proof of the Christiansen-Douglas-Haldane effect in vivo

The Christiansen-Douglas-Haldane effect, in short the Haldane effect, describes the dependence of the CO2 binding of blood on the degree of oxygenation of haemoglobin. Under the physiological conditions of an 'open' system between blood and alveoli the partial pressure of arterial CO2 (PaCO2), must be less than that of mixed venous blood (PvCO2). During the unphysiological conditions of a 'closed' system, e.g. hyperoxic apnoea, i.e. continuous oxygen uptake without CO2 delivery by the lungs, the PaCO2 will not only approximate the PvCO2 but will even exceed it. Without the Haldane effect, rapid adjustment of PaCO2 to PvCO2 would be expected during apnoea due to the lack of CO2 excretion. If, however, as undertaken in this study, ongoing oxygenation (high alveolar PO2 (PACO2) with concomitant lack of CO2 delivery (apnoea, i.e. the CO2 concentration remains constant) lead to a continuing sufficient oxygenation of blood during its passage through the lung capillaries, then this leads to a rightwards shift of the CO2 binding curve--the Haldane effect. The resulting increase in PCO2 as shown here actually leads to an arterial-mixed venous CO2 partial pressure difference (avDPCO2) of 2.8 +/- 1.8 mmHg. The results described substantiate for the first time the existence of the Haldane effect under clinical conditions.

[The washout behavior of isoflurane following balanced anesthesia and its effect on postoperative oxygen supply]

Few studies have described the pharmacokinetics and pharmacodynamics of isoflurane (I) during the postoperative recovery room stay. In this study the influence of balanced anesthesia with I on the postoperative course was investigated by studying pulmonary washout of I and its effect on arterial oxygen saturation. METHODS. Following institutional approval and informed consent, 50 patients (ASA I and II) scheduled for lateral fenestration for intervertebral disc herniation participated; all had no previous record of cardiopulmonary problems. Induction of anesthesia was achieved with intravenous alcuronium 0.03 mg/kg, fentanyl 0.003 mg/kg, thiopental 5 mg/kg, and succinylcholine 1.5 mg/kg followed by alcuronium 0.09 mg/kg before changing to the prone position. Anesthesia was maintained with controlled ventilation in a rebreathing system (fresh gas flow FGF) = 3.01/min, FIO2 = 0.3 in N2O, plus 0.8 Vol.-% cIet = 1.3 MAC). Near the end of surgery I was discontinued and IGI was increased to 61/min O2 for 10 min. Patients then returned to breathing ambient air. Extubation was carried out as soon as a minimum tidal volume of 400 ml was obtained. End tidal I concentration (cIet; Vol.-%) was measured by infrared absorption (Normac, Datex) and O2 saturation by pulse oximetry (Biox III, Ohmeda). Datum point of the pulmonary I-washout curve was the mean end-tidal I concentration obtained 15 min before terminating I (cIAW). Effects of duration of anesthesia, Broca index, and amount of I administered (tidal volume x inspiratory I concentration x min; ml) on I-washout were assessed. A pulse-oximetric O2 saturation of less than 90% was regarded as hypoxygenation. RESULTS. Mean duration of anesthesia for both males and females was 85 +/- 25 min, mean Broca index 102 +/- 13. The amount of I administered with the inspiratory volume was 5.661 +/- 2.194 1 I (1.0 +/- 0.4 Vol.-%). Mean I-regression (Fig. 3) was 236 x 10(-5) Vol.-%/min (Figs. 1 and 3). Mean I-washout 60 min after extubation was 44.6 +/- 15.2% of the administered amount. Adequate spontaneous breathing began a mean of 17 min after the end of I exposure, corresponding to 20% cIet of washout. All patients were extubated after a mean of 22 min at a mean etI of 17% of washout. After extubation, pulse oximetry indicated hypoxygenation in 18 patients (= 36%) during 2 periods (Fig. 4): (1) at a mean cIet of 0.1 Vol.-% (= 15% of washout) after a mean of 8 min; and (2) at a mean cIet of 0.08 Vol.-% (= 12% of washout) a mean of 19 min following extubation. Further episodes of hypoxygenation occurred as much as 40 min post-extubation. (ABSTRACT TRUNCATED AT 400 WORDS)

[Improvement of oxygenation in thoracic surgery with one-lung ventilation using a new intraoperative CPAP device]

For thoracic surgery with one-lung ventilation, the use of CPAP for the non-ventilated lung can improve oxygenation. We studied the use of a newly developed CPAP device in 28 patients undergoing single-lung ventilation. This device was easy to use, in particular because the components are familiar to every anesthesiologist. The use of +5 mbar CPAP improved oxygenation by an average of 39.5 mm Hg; +10 mbar CPAP brought about an improvement of 89 mm Hg. Pulse oximetry proved useful in monitoring adequate oxygenation.

[Fentanyl versus sufentanil basic anesthesia. Hypnotic effect, muscle rigidity and efficacy of competitive muscle relaxants]

As induction agents for cardioanesthesia, sufentanil (S) and fentanyl (F) are usually employed in combination with nondepolarizing muscle relaxants. We investigated potential interactions of these opioids with the relaxant component, paying special regard to the role of muscular rigidity and opioid-induced alterations of hemodynamics. Narcotic anesthesia was induced randomly in 45 coronary artery bypass patients with either F (20 micrograms/kg) or S (4 micrograms/kg). After 6 min, neuromuscular blockade was initiated within each group randomly with either vecuronium (V) or pancuronium (P) (0.01 mg/kg each). During opiate administration, the times for cessation of spontaneous respiration and loss of responsiveness to verbal and tactile stimuli were measured. The degree of opiate-induced muscular rigidity, simultaneous changes in arterial paCO2, cardiac indices (CI) prior to opioid and relaxant administration, onset and recovery from neuromuscular blockade (by electromyographic train-of-four registration), and motor response to laryngoscopy and intubation were recorded. The onset of spontaneous apnea (TK = time to breathing upon command only) and unresponsiveness (TM = time to controlled mask ventilation) was significantly faster with S than with F. Muscular rigidity was moderate in 25% of patients and severe in 35%-40%, during the administration of both narcotics. No significant differences between S and F were observed. During ventilation by face mask, patients with clinically apparent rigidity showed a statistically significant mean increase in paCO2.(ABSTRACT TRUNCATED AT 250 WORDS)

Regional and species differences in vascular reactivity to extracellular potassium

In-vitro vasoreactivity to extracellular potassium (Ko+) was tested in isolated human pial and mesenteric arteries as well as basilar and mesenteric arteries from rabbits and rats. Contractions were induced by stepwise increases in [K+]o and were measured isometrically with a force-displacement transducer, in small-volume organ baths. Significant differences between species as well as between regions were found. The threshold of [K+]o for eliciting contraction in human cerebral arteries in hyperosmotic solutions was 10 mM, in rabbit cerebral arteries 17 mM and in rat cerebral arteries 27 mM. The threshold concentration for contraction in mesenteric arteries was significantly higher compared to cerebral arteries in humans and rabbits, but lower in rats: 20 mM in humans, 26 mM in rabbits and 25 mM in rats. In all species the contractile amplitudes were significantly higher in both cerebral and mesenteric arteries when [K+]o was increased under isotonic conditions in the buffer solution than when hyperosomolality was created. This difference increased with increasing hyperosmolality. In hyperosmotic solutions, the EC50 for [K+]o was lower in cerebral and mesenteric arteries from man than in vessels from rabbit and rat. When the solutions were isotonic, this pattern was seen only in mesenteric arteries. It is concluded that significant species and regional differences in vascular responses to [K+]o exist. Considering that [K+]o is increased in cerebral ischaemia, the observed significantly lower threshold for K+-induced contractions in human cerebral arteries may be of importance, especially in human cerebral ischaemic events.

Transcranial Doppler sonography within 12 hours after subarachnoid hemorrhage

Twenty-one patients were subjected to repeated assessment of cerebral blood flow velocities by means of transcranial Doppler sonography (TCDS) during the first 12 hours after subarachnoid hemorrhage (SAH). In 19 patients the study was performed following the first SAH, and in two after early rebleeds. Flow velocities did not indicate an early phase of arterial narrowing in any case. Following the first TCDS assessment, flows were evaluated repeatedly in the 19 survivors. Increased flow velocities suggesting arterial narrowing or vasospasm occurred only after a delay of at least 4 days. The results of this study favor the restoration of normal velocity patterns in surviving patients and do not indicate that an acute phase of vasospasm exists either immediately after or in the first 12 hours after SAH.